Detection of ground state momenta polarization

The possibility of optical alignment by absorption of angular momenta in the ground state of a molecule was first demonstrated by Drullinger and Zare [124] in 1969. The authors used the Q-transition (X1S = 

For the case of a (P, P)-transition a similar depolarization of radiation with increase in was first registered by the authors of [386] on iodine molecules. In a later paper [369] optical orientation in ground state Na2 molecules in transition (X1E+,v = 2, J = 45 — AlY,+,v b = 14, Jb = 44, at 632.8 nm excitation) was reported, from decrease in circularity prC x) at circularly polarized excitation, by the geometry of Fig. 2.6 (P-transition). The C(w) dependence obtained is presented in Fig. 3.12, where the solid curve is calculated using the corresponding formulae from Table 3.6. 

The problem of passing from the dimensionless parameter x = p/lT, to values of 7s in s-1 has been approached in different ways. The simplest idea is to use extrapolation in the x 1(N) dependence to N = 0, leading to 7coi = 0 and 7s = 70 if one assumes that (3.2) holds. This allows us to obtain Tp = 7ox(0) by evaluating the fly-through relaxation rate 70 as a reciprocal transit time of molecules with the most probable velocity through the effective diameter of the laser beam [102]. 

In a number of studies [150, 151, 178, 368] the value of Tp was determined from the measurements of the absolute fluorescence intensity. Indeed, in the linear limit of weak excitation x — 0, we can obtain from (2.11), (2.23) and (3.18) the intensity for the Q f Q i transition 

knowledge of the concentration of molecules n at level a, the rate Tj/jn of the spontaneous transition b — c, and the upper state b relaxation rate T allows us to determine Tp from the absolute intensity measurements. 

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